Photoresist composition and method of forming photoresist pattern

ABSTRACT

A photoresist composition includes a photoresist material including metal oxide nanoparticles and a ligand, and an acid having an acid dissociation constant, pKa, of −15&lt;pKa&lt;4, or a base having a pKa of 40&gt;pKa&gt;9.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/685,677, filed Jun. 15, 2018, the entire disclosure of which isincorporated herein by reference.

TECHNICAL FIELD

The disclosure relates to photoresist compositions and methods offorming photoresist patterns in a semiconductor manufacturing processes.

BACKGROUND

As consumer devices have gotten smaller and smaller in response toconsumer demand, the individual components of these devices havenecessarily decreased in size as well. Semiconductor devices, which makeup a major component of devices such as mobile phones, computer tablets,and the like, have been pressured to become smaller and smaller, with acorresponding pressure on the individual devices (e.g., transistors,resistors, capacitors, etc.) within the semiconductor devices to also bereduced in size.

One enabling technology that is used in the manufacturing processes ofsemiconductor devices is the use of photosensitive materials. Suchmaterials are applied to a surface and then exposed to an energy thathas itself been patterned. Such an exposure modifies the chemical andphysical properties of the exposed regions of the photosensitivematerial. This modification, along with the lack of modification inregions of the photosensitive that were not exposed, can be exploited toremove one region without removing the other.

However, as the size of individual devices has decreased, processwindows for photolithographic processing have become tighter andtighter. As such, advances in the field of photolithographic processingare necessary to maintain the ability to scale down the devices, andfurther improvements are needed in order to meet the desired designcriteria such that the march towards smaller and smaller components maybe maintained.

Extreme ultraviolet lithography (EUVL) has been developed to formsmaller semiconductor device feature size and increase device density ona semiconductor wafer. As device features shrink the elimination ofdefects becomes more critical. Defects may be formed by variation ofsensitivity and exposure tolerance of the photoresist. Some embodimentsof photoresist compositions have a limited shelf life. As a photoresistcompositions age, the sensitivity and exposure tolerance of thephotoresist varies, leading to variations in the patterns formed, andsubsequently defects.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is best understood from the following detaileddescription when read with the accompanying figures. It is emphasizedthat, in accordance with the standard practice in the industry, variousfeatures are not drawn to scale and are used for illustration purposesonly. In fact, the dimensions of the various features may be arbitrarilyincreased or reduced for clarity of discussion.

FIG. 1 illustrates a process flow of manufacturing a semiconductordevice according to embodiments of the disclosure.

FIG. 2 shows a process stage of a sequential operation according to anembodiment of the disclosure.

FIG. 3 shows a process stage of a sequential operation according to anembodiment of the disclosure.

FIG. 4 shows a process stage of a sequential operation according to anembodiment of the disclosure.

FIG. 5 shows a process stage of a sequential operation according to anembodiment of the disclosure.

FIG. 6 shows a process stage of a sequential operation according to anembodiment of the disclosure.

FIG. 7 shows photoresist polymer components according to embodiments ofthe disclosure.

FIG. 8 shows a process stage of a sequential operation according to anembodiment of the disclosure.

FIG. 9 shows a process stage of a sequential operation according to anembodiment of the disclosure.

FIG. 10 shows a process stage of a sequential operation according to anembodiment of the disclosure.

FIG. 11 shows a process stage of a sequential operation according to anembodiment of the disclosure.

FIG. 12 shows a process stage of a sequential operation according to anembodiment of the disclosure.

FIG. 13 shows a process stage of a sequential operation according to anembodiment of the disclosure.

DETAILED DESCRIPTION

It is to be understood that the following disclosure provides manydifferent embodiments, or examples, for implementing different featuresof the disclosure. Specific embodiments or examples of components andarrangements are described below to simplify the present disclosure.These are, of course, merely examples and are not intended to belimiting. For example, dimensions of elements are not limited to thedisclosed range or values, but may depend upon process conditions and/ordesired properties of the device. Moreover, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed interposing the first and second features, suchthat the first and second features may not be in direct contact. Variousfeatures may be arbitrarily drawn in different scales for simplicity andclarity.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The device may be otherwise oriented (rotated 90 degrees orat other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly. In addition, the term“made of” may mean either “comprising” or “consisting of.”

Increased actinic radiation absorption improves photolithographicpatterning processes. Metal oxides absorb a greater amount of radiation,such as extreme ultraviolet radiation, than organic molecules. Metaloxide nanoparticles are added to photoresists to improve absorption ofactinic radiation, such as extreme ultraviolet radiation. To prevent themetal oxides from separating from the photoresist composition, the metaloxides are complexed by ligands forming a ligand/metal complex. However,the ligand/metal complex is not stable in some photoresist compositions.Initially, each metal oxide nanoparticle may complexed by a plurality ofligand molecules. Over a period of time the photoresist compositionages, ligand molecules separate from the ligand/metal complex, and theinsufficiently complexed or uncomplexed metal oxide nanoparticles mayseparate from the photoresist composition. It is desirable to inhibit orprevent photoresist aging.

FIG. 1 illustrates a process flow 100 of manufacturing a semiconductordevice according to embodiments of the disclosure. A photoresist iscoated on a surface of a layer to be patterned or a substrate 10 inoperation S110, in some embodiments, to form a photoresist layer 15, asshown in FIG. 2. Then the photoresist layer 15 undergoes a first bakingoperation S120 to evaporate solvents in the photoresist composition insome embodiments. The photoresist layer 15 is baked at a temperature andtime sufficient to cure and dry the photoresist layer 15. In someembodiments, the photoresist layer is heated to a temperature of about40° C. to 200° C. for about 10 seconds to about 10 minutes.

After the first baking operation S120, the photoresist layer 15 isselectively exposed to actinic radiation 45 (see FIG. 3) in operationS130. In some embodiments, the photoresist layer 15 is selectivelyexposed to ultraviolet radiation. In some embodiments, the ultravioletradiation is deep ultraviolet radiation. In some embodiments, theultraviolet radiation is extreme ultraviolet (EUV) radiation. In someembodiments, the radiation is an electron beam.

As shown in FIG. 3, the exposure radiation 45 passes through a photomask30 before irradiating the photoresist layer 15 in some embodiments. Insome embodiments, the photomask 30 has a pattern to be replicated in thephotoresist layer 15. The pattern is formed by an opaque pattern 35 onphotomask substrate 40, in some embodiments. The opaque pattern 35 maybe formed by a material opaque to ultraviolet radiation, such aschromium, while the photomask substrate 40 is formed of a material thatis transparent to ultraviolet radiation, such as fused quartz.

The region 50 of the photoresist layer exposed to radiation 45 undergoesa chemical reaction thereby changing its solubility in a subsequentlyapplied developer relative to the region 52 of the photoresist layer 15not exposed to radiation. In some embodiments, the region 50 of thephotoresist layer exposed to radiation 45 becomes more soluble in thedeveloper. In other embodiments, the region 50 of the photoresist layerexposed to radiation 45 becomes less soluble in the developer. In someembodiments, the region 50 of the photoresist layer 15 exposed toradiation undergoes a crosslinking reaction. In other embodiments, theregion 50 of the photoresist layer 15 does not undergo a crosslinkingreaction. In some embodiments, the region 50 of the photoresist layer 15that undergoes a crosslinking reaction is less solube in a developer. Insome embodiments, even though the region 50 of the photoresist exposedto radiation 45 undergoes a crosslinking reaction it is more soluble incertain developers, as will be explained herein.

Next the photoresist layer 15 undergoes a post-exposure bake inoperation S140. In some embodiments, the photoresist layer 15 is heatedto a temperature of about 50° C. and 160° C. for about 20 seconds toabout 120 seconds. The post-exposure baking may be used in order toassist in the generating, dispersing, and reacting of the acid/base/freeradical generated from the impingement of the radiation 45 upon thephotoresist layer 15 during the exposure. Such assistance helps tocreate or enhance chemical reactions which generate chemical differencesbetween the exposed region 50 and the unexposed region 52 within thephotoresist layer 15. These chemical differences also caused differencesin the solubility between the exposed region 50 and the unexposed region52.

The selectively exposed photoresist layer 15 is subsequently developedby applying a developer to the selectively exposed photoresist layer inoperation S150. As shown in FIG. 4, a developer 57 is supplied from adispenser 62 to the photoresist layer 15. In some embodiments, theexposed portion 50 of the photoresist layer 50 is removed by thedeveloper 57 forming a pattern of openings 55 in the photoresist layer15 to expose the substrate 20, as shown in FIG. 5. In other embodiments,the unexposed regions 52 of the photoresist layer are removed by thedeveloper 57, thereby forming a pattern.

In some embodiments, the pattern of openings 55 in the photoresist layer15 are extended into the layer to be patterned or substrate 10 to createa pattern of openings 55′ in the substrate 10, thereby transferring thepattern in the photoresist layer 15 into the substrate 10, as shown inFIG. 6. The pattern is extended into the substrate 10 by etching, usingone or more suitable etchants. The unexposed photoresist layer 15 is atleast partially removed during the etching operation in someembodiments. In other embodiments, the unexposed photoresist layer 15 isremoved after etching the substrate 10 by using a suitable photoresiststripper solvent or by a photoresist ashing operation.

In some embodiments, the substrate 10 includes a single crystallinesemiconductor layer on at least it surface portion. The substrate 10 mayinclude a single crystalline semiconductor material such as, but notlimited to Si, Ge, SiGe, GaAs, InSb, GaP, GaSb, InAlAs, InGaAs, GaSbP,GaAsSb and InP. In some embodiments, the substrate 10 is a silicon layerof an SOI (silicon-on insulator) substrate. In certain embodiments, thesubstrate 10 is made of crystalline Si.

The substrate 10 may include in its surface region, one or more bufferlayers (not shown). The buffer layers can serve to gradually change thelattice constant from that of the substrate to that of subsequentlyformed source/drain regions. The buffer layers may be formed fromepitaxially grown single crystalline semiconductor materials such as,but not limited to Si, Ge, GeSn, SiGe, GaAs, InSb, GaP, GaSb, InAlAs,InGaAs, GaSbP, GaAsSb, GaN, GaP, and InP. In an embodiment, the silicongermanium (SiGe) buffer layer is epitaxially grown on the siliconsubstrate 10. The germanium concentration of the SiGe buffer layers mayincrease from 30 atomic % for the bottom-most buffer layer to 70 atomic% for the top-most buffer layer.

In some embodiments, the substrate 10 includes at least one metal, metalalloy, and metal/nitride/sulfide/oxide/silicide having the formulaMX_(a), where M is a metal and X is N, S, Se, O, Si, and a is from about0.4 to about 2.5. In some embodiments, the substrate 10 includestitanium, aluminum, cobalt, ruthenium, titanium nitride, tungstennitride, tantalum nitride, and combinations thereof.

In some embodiments, the substrate 10 includes a dielectric having atleast silicon, metal oxide, and metal nitride of the formula MX_(b),where M is a metal or Si, X is N or O, and b ranges from about 0.4 toabout 2.5. Ti, Al, Hf, Zr, and La are suitable metals, M, in someembodiments. In some embodiments, the substrate 10 includes silicondioxide, silicon nitride, aluminum oxide, hafnium oxide, lanthanumoxide, and combinations thereof.

The photoresist layer 15 is a photosensitive layer that is patterned byexposure to actinic radiation. Typically, the chemical properties of thephotoresist regions struck by incident radiation change in a manner thatdepends on the type of photoresist used. Photoresist layers 15 aretypically positive resists or negative resists. Positive resist refersto a photoresist material that when exposed to radiation (typically UVlight) becomes soluble in a developer, while the region of thephotoresist that is non-exposed (or exposed less) is insoluble in thedeveloper. Negative resist, on the other hand, refers to a photoresistmaterial that when exposed to radiation becomes insoluble in thedeveloper, while the region of the photoresist that is non-exposed (orexposed less) is soluble in the developer. The region of a negativeresist that becomes insoluble upon exposure to radiation may becomeinsoluble due to a cross-linking reaction caused by the exposure toradiation.

Whether a resist is positive or negative may depend on the type ofdeveloper used to develop the resist. For example, some positivephotoresists provide a positive pattern, (i.e.—the exposed regions areremoved by the developer), when the developer is an aqueous-baseddeveloper, such as a tetramethylammonium hydroxide (TMAH) solution. Onthe other hand, the same photoresist provides a negative pattern(i.e.—the unexposed regions are removed by the developer) when thedeveloper is an organic solvent. Further, in some negative photoresistsdeveloped with the TMAH solution, the unexposed regions of thephotoresist are removed by the TMAH, and the exposed regions of thephotoresist, that undergo cross-linking upon exposure to actinicradiation, remain on the substrate after development. In someembodiments of the present disclosure, a negative photoresist is exposedto actinic radiation. The exposed portions of the negative photoresistundergo crosslinking as a result of the exposure to actinic radiation,and during development the exposed, crosslinked portions of thephotoresist are removed by the developer leaving the unexposed regionsof the photoresist remaining on the substrate.

In an embodiment, the photoresist layer 15 is a negative photoresistthat undergoes a cross-linking reaction upon exposure to the radiation.Photoresists according to the present disclosure include a polymer resinalong with one or more photoactive compounds (PACs) in a solvent, insome embodiments. In some embodiments, the polymer resin includes ahydrocarbon structure (such as an alicyclic hydrocarbon structure) thatcontains one or more groups that will decompose (e.g., acid labilegroups) or otherwise react when mixed with acids, bases, or freeradicals generated by the PACs (as further described below). In someembodiments, the hydrocarbon structure includes a repeating unit thatforms a skeletal backbone of the polymer resin. This repeating unit mayinclude acrylic esters, methacrylic esters, crotonic esters, vinylesters, maleic diesters, fumaric diesters, itaconic diesters,(meth)acrylonitrile, (meth)acrylamides, styrenes, vinyl ethers,combinations of these, or the like.

Specific structures that are utilized for the repeating unit of thehydrocarbon structure in some embodiments, include one or more of methylacrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butylacrylate, isobutyl acrylate, tert-butyl acrylate, n-hexyl acrylate,2-ethylhexyl acrylate, acetoxyethyl acrylate, phenyl acrylate,2-hydroxyethyl acrylate, 2-methoxyethyl acrylate, 2-ethoxyethylacrylate, 2-(2-methoxyethoxy)ethyl acrylate, cyclohexyl acrylate, benzylacrylate, 2-alkyl-2-adamantyl (meth)acrylate ordialkyl(1-adamantyl)methyl (meth)acrylate, methyl methacrylate, ethylmethacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butylmethacrylate, isobutyl methacrylate, tert-butyl methacrylate, n-hexylmethacrylate, 2-ethylhexyl methacrylate, acetoxyethyl methacrylate,phenyl methacrylate, 2-hydroxyethyl methacrylate, 2-methoxyethylmethacrylate, 2-ethoxyethyl methacrylate, 2-(2-methoxyethoxy)ethylmethacrylate, cyclohexyl methacrylate, benzyl methacrylate,3-chloro-2-hydroxypropyl methacrylate, 3-acetoxy-2-hydroxypropylmethacrylate, 3-chloroacetoxy-2-hydroxypropyl methacrylate, butylcrotonate, hexyl crotonate, or the like. Examples of the vinyl estersinclude vinyl acetate, vinyl propionate, vinyl butylate, vinylmethoxyacetate, vinyl benzoate, dimethyl maleate, diethyl maleate,dibutyl maleate, dimethyl fumarate, diethyl fumarate, dibutyl fumarate,dimethyl itaconate, diethyl itaconate, dibutyl itaconate, acrylamide,methyl acrylamide, ethyl acrylamide, propyl acrylamide, n-butylacrylamide, tert-butyl acrylamide, cyclohexyl acrylamide, 2-methoxyethylacrylamide, dimethyl acrylamide, diethyl acrylamide, phenyl acrylamide,benzyl acrylamide, methacrylamide, methyl methacrylamide, ethylmethacrylamide, propyl methacrylamide, n-butyl methacrylamide,tert-butyl methacrylamide, cyclohexyl methacrylamide, 2-methoxyethylmethacrylamide, dimethyl methacrylamide, diethyl methacrylamide, phenylmethacrylamide, benzyl methacrylamide, methyl vinyl ether, butyl vinylether, hexyl vinyl ether, methoxyethyl vinyl ether, dimethylaminoethylvinyl ether, or the like. Examples of styrenes include styrene, methylstyrene, dimethyl styrene, trimethyl styrene, ethyl styrene, isopropylstyrene, butyl styrene, methoxy styrene, butoxy styrene, acetoxystyrene, chloro styrene, dichloro styrene, bromo styrene, vinyl methylbenzoate, α-methyl styrene, maleimide, vinylpyridine, vinylpyrrolidone,vinylcarbazole, combinations of these, or the like.

In some embodiments, the repeating unit of the hydrocarbon structurealso has either a monocyclic or a polycyclic hydrocarbon structuresubstituted into it, or the monocyclic or polycyclic hydrocarbonstructure is the repeating unit, in order to form an alicyclichydrocarbon structure. Specific examples of monocyclic structures insome embodiments include bicycloalkane, tricycloalkane,tetracycloalkane, cyclopentane, cyclohexane, or the like. Specificexamples of polycyclic structures in some embodiments includeadamantane, norbornane, isobornane, tricyclodecane, tetracyclododecane,or the like.

The group which will decompose, otherwise known as a leaving group or,in some embodiments in which the PAC is a photoacid generator, an acidlabile group, is attached to the hydrocarbon structure so that, it willreact with the acids/bases/free radicals generated by the PACs duringexposure. In some embodiments, the group which will decompose is acarboxylic acid group, a fluorinated alcohol group, a phenolic alcoholgroup, a sulfonic group, a sulfonamide group, a sulfonylimido group, an(alkylsulfonyl) (alkylcarbonyl)methylene group, an(alkylsulfonyl)(alkyl-carbonyl)imido group, abis(alkylcarbonyl)methylene group, a bis(alkylcarbonyl)imido group, abis(alkylsylfonyl)methylene group, a bis(alkylsulfonyl)imido group, atris(alkylcarbonyl methylene group, a tris(alkylsulfonyl)methylenegroup, combinations of these, or the like. Specific groups that are usedfor the fluorinated alcohol group include fluorinated hydroxyalkylgroups, such as a hexafluoroisopropanol group in some embodiments.Specific groups that are used for the carboxylic acid group includeacrylic acid groups, methacrylic acid groups, or the like.

In some embodiments, the polymer resin also includes other groupsattached to the hydrocarbon structure that help to improve a variety ofproperties of the polymerizable resin. For example, inclusion of alactone group to the hydrocarbon structure assists to reduce the amountof line edge roughness (LER) after the photoresist has been developed,thereby helping to reduce the number of defects that occur duringdevelopment. In some embodiments, the lactone groups include ringshaving five to seven members, although any suitable lactone structuremay alternatively be used for the lactone group.

In some embodiments, the polymer resin includes groups that can assistin increasing the adhesiveness of the photoresist layer 15 to underlyingstructures (e.g., substrate 10). Polar groups may be used to helpincrease the adhesiveness. Suitable polar groups include hydroxylgroups, cyano groups, or the like, although any suitable polar groupmay, alternatively, be used.

Optionally, the polymer resin includes one or more alicyclic hydrocarbonstructures that do not also contain a group which will decompose in someembodiments. In some embodiments, the hydrocarbon structure that doesnot contain a group which will decompose includes structures such as1-adamantyl (meth)acrylate, tricyclodecanyl (meth)acrylate, cyclohexyl(methacrylate), combinations of these, or the like.

In some embodiments, the amount of polymer resin in the photoresistcomposition ranges from about 1 wt. % to about 15 wt. % based on theweight of the solvent for the photoresist composition. If theconcentration of the polymer resin is less than about 1 wt. % thephotoresist coating will be too thin. If the concentration of thepolymer resin is greater than about 15 wt. % the photoresist compositionis too viscous and it will be difficult to provide a photoresist coatingof uniform thickness on the substrate. In some embodiments, the amountof polymer resin in the photoresist composition ranges from about 2 wt.% to about 10 wt. % based on the weight of the solvent. In otherembodiments, the amount of polymer resin ranges from about 3 wt. % toabout 7 wt. % based on the weight of the solvent.

Additionally, embodiments of the photoresist include one or morephotoactive compounds (PACs). The PACs are photoactive components, suchas photoacid generators, photobase generators, free-radical generators,or the like. The PACs may be positive-acting or negative-acting. In someembodiments in which the PACs are a photoacid generator, the PACsinclude halogenated triazines, onium salts, diazonium salts, aromaticdiazonium salts, phosphonium salts, sulfonium salts, iodonium salts,imide sulfonate, oxime sulfonate, diazodisulfone, disulfone,o-nitrobenzylsulfonate, sulfonated esters, halogenated sulfonyloxydicarboximides, diazodisulfones, α-cyanooxyamine-sulfonates,imidesulfonates, ketodiazosulfones, sulfonyldiazoesters,1,2-di(arylsulfonyl)hydrazines, nitrobenzyl esters, and the s-triazinederivatives, combinations of these, or the like.

Specific examples of photoacid generators includeα-(trifluoromethylsulfonyloxy)-bicyclo[2.2.1]hept-5-ene-2,3-dicarb-o-ximide(MDT), N-hydroxy-naphthalimide (DDSN), benzoin tosylate,t-butylphenyl-α-(p-toluenesulfonyloxy)-acetate andt-butyl-α-(p-toluenesulfonyloxy)-acetate, triarylsulfonium anddiaryliodonium hexafluoroantimonates, hexafluoroarsenates,trifluoromethanesulfonates, iodonium perfluorooctanesulfonate,N-camphorsulfonyloxynaphthalimide,N-pentafluorophenylsulfonyloxynaphthalimide, ionic iodonium sulfonatessuch as diaryl iodonium (alkyl or aryl)sulfonate andbis-(di-t-butylphenyl)iodonium camphanylsulfonate,perfluoroalkanesulfonates such as perfluoropentanesulfonate,perfluorooctanesulfonate, perfluoromethanesulfonate, aryl (e.g., phenylor benzyl)triflates such as triphenylsulfonium triflate orbis-(t-butylphenyl)iodonium triflate; pyrogallol derivatives (e.g.,trimesylate of pyrogallol), trifluoromethanesulfonate esters ofhydroxyimides, α,α′-bis-sulfonyl-diazomethanes, sulfonate esters ofnitro-substituted benzyl alcohols, naphthoquinone-4-diazides, alkyldisulfones, or the like.

In some embodiments in which the PACs are free-radical generators, thePACs include n-phenylglycine; aromatic ketones, including benzophenone,N,N′-tetramethyl-4,4′-diaminobenzophenone,N,N′-tetraethyl-4,4′-diaminobenzophenone,4-methoxy-4′-dimethylaminobenzo-phenone,3,3′-dimethyl-4-methoxybenzophenone,p,p′-bis(dimethylamino)benzo-phenone,p,p′-bis(diethylamino)-benzophenone; anthraquinone,2-ethylanthraquinone; naphthaquinone; and phenanthraquinone; benzoinsincluding benzoin, benzoinmethylether, benzoinisopropylether,benzoin-n-butylether, benzoin-phenylether, methylbenzoin andethylbenzoin; benzyl derivatives, including dibenzyl,benzyldiphenyldisulfide, and benzyldimethylketal; acridine derivatives,including 9-phenylacridine, and 1,7-bis(9-acridinyl)heptane;thioxanthones, including 2-chlorothioxanthone, 2-methylthioxanthone,2,4-diethylthioxanthone, 2,4-dimethylthioxanthone, and2-isopropylthioxanthone; acetophenones, including1,1-dichloroacetophenone, p-t-butyldichloro-acetophenone,2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, and2,2-dichloro-4-phenoxyacetophenone; 2,4,5-triarylimidazole dimers,including 2-(o-chlorophenyl)-4,5-diphenylimidazole dimer,2-(o-chlorophenyl)-4,5-di-(m-methoxyphenyl imidazole dimer,2-(o-fluorophenyl)-4,5-diphenylimidazole dimer,2-(o-methoxyphenyl)-4,5-diphenylimidazole dimer,2-(p-methoxyphenyl)-4,5-diphenylimidazole dimer,2,4-di(p-methoxyphenyl)-5-phenylimidazole dimer,2-(2,4-dimethoxyphenyl)-4,5-diphenylimidazole dimer and2-(p-methylmercaptophenyl)-4,5-diphenylimidazole dimmer; combinations ofthese, or the like.

In some embodiments in which the PACs are photobase generators, the PACsincludes quaternary ammonium dithiocarbamates, a aminoketones,oxime-urethane containing molecules such as dibenzophenoneoximehexamethylene diurethan, ammonium tetraorganylborate salts, andN-(2-nitrobenzyloxycarbonyl)cyclic amines, combinations of these, or thelike.

In some embodiments, the photoresist composition includes about 1 wt. %to about 10 wt. % of a photoactive compound (PAC) based on the weight ofthe polymer resin. If the concentration of the photoactive compound isless than about 1 wt. % it will not have the desired effect of improvingthe photosensitivity of the photoresist composition. A concentration ofthe photoactive compound greater than about 10 wt. % will not provide asignificant improvement in photosensitivity over a concentration ofabout 10 wt. %.

As one of ordinary skill in the art will recognize, the chemicalcompounds listed herein are merely intended as illustrated examples ofthe PACs and are not intended to limit the embodiments to only thosePACs specifically described. Rather, any suitable PAC may be used, andall such PACs are fully intended to be included within the scope of thepresent embodiments.

In some embodiments, a cross-linking agent is added to the photoresist.The cross-linking agent reacts with one group from one of thehydrocarbon structures in the polymer resin and also reacts with asecond group from a separate one of the hydrocarbon structures in orderto cross-link and bond the two hydrocarbon structures together. Thisbonding and cross-linking increases the molecular weight of the polymerproducts of the cross-linking reaction and increases the overall linkingdensity of the photoresist. Such an increase in density and linkingdensity helps to improve the resist pattern. In some embodiments, thephotoresist composition includes about 1 wt. % to about 20 wt. % of thecross-linking agent based on the weight of the polymer resin. In someembodiments, the photoresist composition includes about 1 wt. % to about10 wt. % of the cross-linking agent based on the weight of the polymerresin. Concentrations of the cross-linking agent less than about 1 wt. %provide insufficient cross-linking effect. Concentrations of thecross-linking agent greater than about 20 wt. % will not provide anybeneficial effect over a concentration of about 20 wt. % cross-linkingagent.

In some embodiments the cross-linking agent has the following structure:

wherein C is carbon, n ranges from 1 to 15; A and B independentlyinclude a hydrogen atom, a hydroxyl group, a halide, an aromatic carbonring, or a straight or cyclic alkyl, alkoxyl/fluoro, alkyl/fluoroalkoxylchain having a carbon number of between 1 and 12, and each carbon Ccontains A and B; a first terminal carbon C at a first end of a carbon Cchain includes X and a second terminal carbon C at a second end of thecarbon chain includes Y, wherein X and Y independently include an aminegroup, a thiol group, a hydroxyl group, an isopropyl alcohol group, oran isopropyl amine group, except when n=1 then X and Y are bonded to thesame carbon C. Specific examples of materials that may be used as thecross-linking agent include the following:

Alternatively, instead of or in addition to the cross-linking agentbeing added to the photoresist composition, a coupling reagent is addedin some embodiments, in which the coupling reagent is added in additionto the cross-linking agent. The coupling reagent assists thecross-linking reaction by reacting with the groups on the hydrocarbonstructure in the polymer resin before the cross-linking reagent,allowing for a reduction in the reaction energy of the cross-linkingreaction and an increase in the rate of reaction. The bonded couplingreagent then reacts with the cross-linking agent, thereby coupling thecross-linking agent to the polymer resin. In some embodiments, thephotoresist composition includes about 1 wt. % to about 20 wt. % of thecoupling reagent based on the weight of the polymer resin.Concentrations of the coupling reagent less than about 1 wt. % provideinsufficient assistance to the cross-linking. Concentrations of thecross-linking agent greater than about 20 wt. % will not provide asignificant improvement assistance to cross-linking over a concentrationof about 20 wt. %.

Alternatively, in some embodiments in which the coupling reagent isadded to the photoresist without the cross-linking agent, the couplingreagent is used to couple one group from one of the hydrocarbonstructures in the polymer resin to a second group from a separate one ofthe hydrocarbon structures in order to cross-link and bond the twopolymers together. However, in such an embodiment the coupling reagent,unlike the cross-linking agent, does not remain as part of the polymer,and only assists in bonding one hydrocarbon structure directly toanother hydrocarbon structure.

In some embodiments, the coupling reagent has the following structure:

where R is a carbon atom, a nitrogen atom, a sulfur atom, or an oxygenatom; M includes a chlorine atom, a bromine atom, an iodine atom, —NO₂;—SO₃—; —H; —CN; —NCO, —OCN; —CO₂—; —OH; —OR*, —OC(O)CR*; —SR,—SO2N(R*)₂; —SO₂R*; —SOR; —OC(O)R*; —C(O)OR*; —C(O)R*; —Si(OR*)₃;—Si(R*)₃; epoxy groups, or the like; and R* is a substituted orunsubstituted C1-C12 alkyl, C1-C12 aryl, C1-C12 aralkyl, or the like.Specific examples of materials used as the coupling reagent in someembodiments include the following:

In some embodiments, the photoresist includes a protective polymer thatforms a protective layer when applied to a layer to be patterned orsubstrate 10, as described in U.S. application Ser. No. 15/994,615,incorporated herein by reference in its entirety. The protective layerprevents contaminants, including particles, moisture, and ammonia, frombeing absorbed into or impregnating the photoresist layer 15. In someembodiments, the protective polymer has fluorocarbon pendant groups. Inan embodiment, a main chain of the polymer having fluorocarbon pendantgroups is a polyhydroxystyrene, a polyacrylate, or a polymer formed froma 1 to 10 carbon monomer. In an embodiment, the polymer havingfluorocarbon pendant groups includes from about 0.1 wt. % to about 10wt. % of one or more polar functional groups selected from the groupconsisting —OH, —NH₃, —NH₂, and —SO₃ based on the total weight of thepolymer having fluorocarbon pendant groups. In an embodiment, thepolymer having fluorocarbon pendant groups includes from about 0.1 wt. %to about 10 wt. % of the fluorocarbon pendant groups based on the totalweight of the polymer having fluorocarbon pendant groups. Less thanabout 0.1 wt. % of the fluorocarbon pendant groups does not provide asignificant improvement in the protective layer of the photoresistcomposition. Greater than about 10 wt. % of the fluorocarbon pendantswill not provide a significant improvement in the protective layer overa concentration of about 10 wt. %.

In an embodiment, the fluorocarbon pendant groups are attached to apolymer main chain via a linking unit R1 of at least one selected fromthe group consisting of 1-9 carbon unbranched, branched, cyclic,noncylic, saturated, or unsaturated hydrocarbon with optional halogensubstituents; —S—; —P—; —P(O₂); —C(═O)S—; —C(═O)O—; —O—; —N—; —C(═O)N—;—SO₂O—; —SO₂S—; —SO—; —SO₂—; and —C(═O)—. In an embodiment, thefluorocarbon pendant group is selected from the group consisting ofC_(x)F_(y), where 1≤x≤9 and 3≤y≤12; and —(C(CF₃)₂OH)—. Examples ofC_(x)F_(y) units attached to the polymer chain via a linking unit R1according to embodiments of the disclosure are shown in FIG. 7. Asshown, in some embodiments, C_(x)F_(y) is one or more selected from thegroup consisting of —C₂F₅, —CH₂CH₂C₃F₇, —(C(CF₃)₂OH), —CH₂OC₄F₉, and—C(═O)O(C(CF₃)₂OH).

In some embodiments, the amount of protective polymer havingfluorocarbon pendant groups in the photoresist/protective polymermixture ranges from about 1 wt. % to about 10 wt. % based on the totalweight of the photoresist/protective polymer mixture. In someembodiments, the protective polymer having fluorocarbon pendant groupshas a weight average molecular weight of about 3000 to about 15,000. Insome embodiments, the protective polymer having fluorocarbon pendantgroups has a weight average molecular weight of about 6000 to about11,000. In some embodiments, the protective layer has a thicknessranging from about 0.1 nm to about 20 nm. In some embodiments, thethickness of the protective layer ranges from about 1 nm to about 15 nm.In some embodiments, the contact angle of the protective layer to wateris greater than 75°.

The individual components of the photoresist are placed into a solventin order to aid in the mixing and dispensing of the photoresist. To aidin the mixing and dispensing of the photoresist, the solvent is chosenat least in part based upon the materials chosen for the polymer resinsas well as the PACs. In some embodiments, the solvent is chosen suchthat the polymer resins and the PACs can be evenly dissolved into thesolvent and dispensed upon the layer to be patterned.

In some embodiments, the solvent is an organic solvent, and includes oneor more of any suitable solvent such as ketones, alcohols, polyalcohols,ethers, glycol ethers, cyclic ethers, aromatic hydrocarbons, esters,propionates, lactates, lactic esters, alkylene glycol monoalkyl ethers,alkyl lactates, alkyl alkoxypropionates, cyclic lactones, monoketonecompounds that contain a ring, alkylene carbonates, alkyl alkoxyacetate,alkyl pyruvates, lactate esters, ethylene glycol alkyl ether acetates,diethylene glycols, propylene glycol alkyl ether acetates, alkyleneglycol alkyl ether esters, alkylene glycol monoalkyl esters, or thelike.

Specific examples of materials that may be used as the solvent for thephotoresist include, acetone, methanol, ethanol, toluene, xylene,4-hydroxy-4-methyl-2-pentatone, tetrahydrofuran, methyl ethyl ketone,cyclohexanone, methyl isoamyl ketone, 2-heptanone, ethylene glycol,ethylene glycol monoacetate, ethylene glycol dimethyl ether, ethyleneglycol dimethyl ether, ethylene glycol methylethyl ether, ethyleneglycol monoethyl ether, methyl cellosolve acetate, ethyl cellosolveacetate, diethylene glycol, diethylene glycol monoacetate, diethyleneglycol monomethyl ether, diethylene glycol diethyl ether, diethyleneglycol dimethyl ether, diethylene glycol ethylmethyl ether,diethethylene glycol monoethyl ether, diethylene glycol monobutyl ether,ethyl 2-hydroxypropionate, methyl 2-hydroxy-2-methylpropionate, ethyl2-hydroxy-2-methylpropionate, ethyl ethoxyacetate, ethyl hydroxyacetate,methyl 2-hydroxy-2-methylbutanate, methyl 3-methoxypropionate, ethyl3-methoxypropionate, methyl 3-ethoxypropionate, ethyl3-ethoxypropionate, methyl acetate, ethyl acetate, propyl acetate, butylacetate, methyl lactate, ethyl lactate, propyl lactate, butyl lactate,propylene glycol, propylene glycol monoacetate, propylene glycolmonoethyl ether acetate, propylene glycol monomethyl ether acetate,propylene glycol monopropyl methyl ether acetate, propylene glycolmonobutyl ether acetate, propylene glycol monobutyl ether acetate,propylene glycol monomethyl ether propionate, propylene glycol monoethylether propionate, propylene glycol methyl ether acetate, propyleneglycol ethyl ether acetate, ethylene glycol monomethyl ether acetate,ethylene glycol monoethyl ether acetate, propylene glycol monomethylether, propylene glycol monoethyl ether, propylene glycol monopropylether, propylene glycol monobutyl ether, ethylene glycol monomethylether, ethylene glycol monoethyl ether, ethyl 3-ethoxypropionate, methyl3-methoxypropionate, methyl 3-ethoxypropionate, and ethyl3-methoxypropionate, β-propiolactone, β-butyrolactone, γ-butyrolactone,α-methyl-γ-butyrolactone, β-methyl-γ-butyrolactone, γ-valerolactone,γ-caprolactone, γ-octanoic lactone, α-hydroxy-γ-butyrolactone,2-butanone, 3-methylbutanone, pinacolone, 2-pentanone, 3-pentanone,4-methyl-2-pentanone, 2-methyl-3-pentanone, 4,4-dimethyl-2-pentanone,2,4-dimethyl-3-pentanone, 2,2,4,4-tetramethyl-3-pentanone, 2-hexanone,3-hexanone, 5-methyl-3-hexanone, 2-heptanone, 3-heptanone, 4-heptanone,2-methyl-3-heptanone, 5-methyl-3-heptanone, 2,6-dimethyl-4-heptanone,2-octanone, 3-octanone, 2-nonanone, 3-nonanone, 5-nonanone, 2-decanone,3-decanone, 4-decanone, 5-hexene-2-one, 3-pentene-2-one, cyclopentanone,2-methylcyclopentanone, 3-methylcyclopentanone,2,2-dimethylcyclopentanone, 2,4,4-trimethylcyclopentanone,cyclohexanone, 3-methylcyclohexanone, 4-methylcyclohexanone,4-ethylcyclohexanone, 2,2-dimethylcyclohexanone,2,6-dimethylcyclohexanone, 2,2,6-trimethylcyclohexanone, cycloheptanone,2-methylcycloheptanone, 3-methylcycloheptanone, propylene carbonate,vinylene carbonate, ethylene carbonate, butylene carbonate,acetate-2-methoxyethyl, acetate-2-ethoxyethyl,acetate-2-(2-ethoxyethoxy)ethyl, acetate-3-methoxy-3-methylbutyl,acetate-1-methoxy-2-propyl, dipropylene glycol, monomethylether,monoethylether, monopropylether, monobutylether, monophenylether,dipropylene glycol monoacetate, dioxane, methyl pyruvate, ethylpyruvate, propyl pyruvate, methyl methoxypropionate, ethylethoxypropionate, n-methylpyrrolidone (NMP), 2-methoxyethyl ether(diglyme), ethylene glycol monomethyl ether, propylene glycol monomethylether, methyl propionate, ethyl propionate, ethyl ethoxy propionate,methylethyl ketone, cyclohexanone, 2-heptanone, cyclopentanone,cyclohexanone, ethyl 3-ethoxypropionate, propylene glycol methyl etheracetate (PGMEA), methylene cellosolve, 2-ethoxyethanol,N-methylformamide, N,N-dimethylformamide, N-methylformanilide,N-methylacetamide, N,N-dimethylacetamide, dimethylsulfoxide, benzylethyl ether, dihexyl ether, acetonylacetone, isophorone, caproic acid,caprylic acid, 1-octanol, 1-nonanol, benzyl alcohol, benzyl acetate,ethyl benzoate, diethyl oxalate, diethyl maleate, phenyl cellosolveacetate, or the like.

In some embodiments, the solvent is selected from the group consistingof dimethylsulfoxide, acetone, ethylene glycol, methanol, ethanol,propanol, isopropanol, propanediol, water, 4-methyl-2-pentanone,hydrogen peroxide, butyldiglycol, and combinations thereof.

As one of ordinary skill in the art will recognize, the materials listedand described above as examples of materials that may be used for thesolvent component of the photoresist are merely illustrative and are notintended to limit the embodiments. Rather, any suitable materials thatdissolve the polymer resin and the PACs may be used to help mix andapply the photoresist. All such materials are fully intended to beincluded within the scope of the embodiments.

Additionally, while individual ones of the above described materials maybe used as the solvent for the photoresist and protective polymer, inother embodiments more than one of the above described materials areused. For example, in some embodiments, the solvent includes acombination mixture of two or more of the materials described. All suchcombinations are fully intended to be included within the scope of theembodiments.

In addition to the polymer resins, the PACs, the solvents, thecross-linking agent, and the coupling reagent, some embodiments of thephotoresist also include a number of other additives that assist thephotoresist to obtain high resolution. For example, some embodiments ofthe photoresist also include surfactants in order to help improve theability of the photoresist to coat the surface on which it is applied.In some embodiments, the surfactants include nonionic surfactants,polymers having fluorinated aliphatic groups, surfactants that containat least one fluorine atom and/or at least one silicon atom,polyoxyethylene alkyl ethers, polyoxyethylene alkyl aryl ethers,polyoxyethylene-polyoxypropylene block copolymers, sorbitan fatty acidesters, and polyoxyethylene sorbitan fatty acid esters.

Specific examples of materials used as surfactants in some embodimentsinclude polyoxyethylene lauryl ether, polyoxyethylene stearyl ether,polyoxyethylene cetyl ether, polyoxyethylene oleyl ether,polyoxyethylene octyl phenol ether, polyoxyethylene nonyl phenol ether,sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate,sorbitan monooleate, sorbitan trioleate, sorbitan tristearate,polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitanmonopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylenesorbitan trioleate, polyoxyethylene sorbitan tristearate, polyethyleneglycol distearate, polyethylene glycol dilaurate, polyethylene glycoldilaurate, polyethylene glycol, polypropylene glycol,polyoxyethylenestearyl ether, polyoxyethylene cetyl ether, fluorinecontaining cationic surfactants, fluorine containing nonionicsurfactants, fluorine containing anionic surfactants, cationicsurfactants and anionic surfactants, polyethylene glycol, polypropyleneglycol, polyoxyethylene cetyl ether, combinations thereof, or the like.In some embodiments, the photoresist composition contains from about0.001 wt. % to about 1 wt. % of the surfactant based on the total weightof the photoresist composition.

Another additive in some embodiments of the photoresist is a dissolutioninhibitor to help control dissolution of the photoresist duringdevelopment. In an embodiment bile-salt esters may be utilized as thedissolution inhibitor. Specific examples of dissolution inhibitors insome embodiments include cholic acid, deoxycholic acid, lithocholicacid, t-butyl deoxycholate, t-butyl lithocholate, and t-butyl-3-acetyllithocholate. In some embodiments, the photoresist composition containsfrom about 0.001 wt. % to about 1 wt. % of the dissolution inhibitorbased on the total weight of the photoresist composition.

Another additive in some embodiments of the photoresist is aplasticizer. Plasticizers may be used to reduce delamination andcracking between the photoresist and underlying layers (e.g., the layerto be patterned). Plasticizers include monomeric, oligomeric, andpolymeric plasticizers, such as oligo- and polyethyleneglycol ethers,cycloaliphatic esters, and non-acid reactive steroidaly-derivedmaterials. Specific examples of materials used for the plasticizer insome embodiments include dioctyl phthalate, didodecyl phthalate,triethylene glycol dicaprylate, dimethyl glycol phthalate, tricresylphosphate, dioctyl adipate, dibutyl sebacate, triacetyl glycerine, orthe like. In some embodiments, the photoresist composition contains fromabout 0.001 wt. % to about 1 wt. % of the plasticizer based on the totalweight of the photoresist composition.

A coloring agent is another additive included in some embodiments of thephotoresist. The coloring agent observers examine the photoresist andfind any defects that may need to be remedied prior to furtherprocessing. In some embodiments, the coloring agent is a triarylmethanedye or a fine particle organic pigment. Specific examples of materialsin some embodiments include crystal violet, methyl violet, ethyl violet,oil blue #603, Victoria Pure Blue BOH, malachite green, diamond green,phthalocyanine pigments, azo pigments, carbon black, titanium oxide,brilliant green dye (C. I. 42020), Victoria Pure Blue FGA (Linebrow),Victoria BO (Linebrow) (C. I. 42595), Victoria Blue BO (C. I. 44045),rhodamine 6G (C. I. 45160), benzophenone compounds, such as2,4-dihydroxybenzophenone and 2,2′,4,4′-tetrahydroxybenzophenone;salicylic acid compounds, such as phenyl salicylate and 4-t-butylphenylsalicylate; phenylacrylate compounds, such asethyl-2-cyano-3,3-diphenylacrylate, and2′-ethylhexyl-2-cyano-3,3-diphenylacrylate; benzotriazole compounds,such as 2-(2-hydroxy-5-methylphenyl)-2H-benzotriazole, and2-(3-t-butyl-2-hydroxy-5-methylphenyl)-5-chloro-2H-benzotriazole;coumarin compounds, such as 4-methyl-7-diethylamino-1-benzopyran-2-one;thioxanthone compounds, such as diethylthioxanthone; stilbene compounds,naphthalic acid compounds, azo dyes, phthalocyanine blue, phthalocyaninegreen, iodine green, Victoria blue, crystal violet, titanium oxide,naphthalene black, Photopia methyl violet, bromphenol blue andbromcresol green; laser dyes, such as Rhodamine G6, Coumarin 500, DCM(4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H pyran)),Kiton Red 620, Pyrromethene 580, or the like. Additionally, one or morecoloring agents may be used in combination to provide the desiredcoloring. In some embodiments, the photoresist composition contains fromabout 0.001 wt. % to about 1 wt. % of the coloring agent based on thetotal weight of the photoresist composition.

Adhesion additives are added to some embodiments of the photoresist topromote adhesion between the photoresist and an underlying layer uponwhich the photoresist has been applied (e.g., the layer to bepatterned). In some embodiments, the adhesion additives include a silanecompound with at least one reactive substituent such as a carboxylgroup, a methacryloyl group, an isocyanate group and/or an epoxy group.Specific examples of the adhesion components include trimethoxysilylbenzoic acid, γ-methacryloxypropyl trimethoxy silane,vinyltriacetoxysilane, vinyltrimethoxysilane, γ-isocyanatepropyltriethoxy silane, γ-glycidoxypropyl trimethoxy silane,β-(3,4-epoxycyclohexyl)ethyl trimethoxy silane, benzimidazoles andpolybenzimidazoles, a lower hydroxyalkyl substituted pyridinederivative, a nitrogen heterocyclic compound, urea, thiourea, anorganophosphorus compound, 8-oxyquinoline, 4-hydroxypteridine andderivatives, 1,10-phenanthroline and derivatives, 2,2′-bipyridine andderivatives, benzotriazoles, organophosphorus compounds,phenylenediamine compounds, 2-amino-1-phenylethanol,N-phenylethanolamine, N-ethyldiethanolamine, N-ethylethanolamine andderivatives, benzothiazole, and a benzothiazoleamine salt having acyclohexyl ring and a morpholine ring,3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane,3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane,3-methacryloyloxypropyltrimethoxysilane, vinyl trimethoxysilane,combinations thereof, or the like. In some embodiments, the photoresistcomposition contains from about 0.001 wt. % to about 1 wt. % of theadhesion additive based on the total weight of the photoresistcomposition.

Surface leveling agents are added to some embodiments of the photoresistto assist a top surface of the photoresist to be level, so thatimpinging light will not be adversely modified by an unlevel surface. Insome embodiments, surface leveling agents include fluoroaliphaticesters, hydroxyl terminated fluorinated polyethers, fluorinated ethyleneglycol polymers, silicones, acrylic polymer leveling agents,combinations thereof, or the like. In some embodiments, the photoresistcomposition contains from about 0.001 wt. % to about 1 wt. % of thesurface leveling agents based on the total weight of the photoresistcomposition.

Some embodiments of the photoresist include metal oxide nanoparticles.The metal oxide nanoparticles improve actinic radiation absorption insome embodiments. In some embodiments, the photoresist includes one ormore metal oxides nanoparticles selected from the group consisting oftitanium dioxide, zinc oxide, zirconium dioxide, nickel oxide, cobaltoxide, manganese oxide, copper oxides, iron oxides, strontium titanate,tungsten oxides, vanadium oxides, chromium oxides, tin oxides, hafniumoxide, indium oxide, cadmium oxide, molybdenum oxide, tantalum oxides,niobium oxide, aluminum oxide, and combinations thereof. As used herein,nanoparticles are particles having an average particle size betweenabout 1 nm and about 20 nm. Metal oxide nanoparticle sizes less thanabout 1 nm are difficult to obtain and use in photoresist compositions.Metal oxide nanoparticles greater than about 20 nm are too large for usein a resist in embodiments of the disclosure. In some embodiments themetal oxide nanoparticles have an average particle size between about 2and about 5 nm. In some embodiments, the amount of metal oxidenanoparticles in the photoresist composition ranges from about 1 wt. %to about 15 wt. % based on the weight of the solvent for the photoresistcomposition. In some embodiments, the amount of nanoparticles in thephotoresist composition ranges from about 2 wt. % to about 10 wt. %based on the weight of the solvent for the photoresist composition.Concentrations of the metal oxide nanoparticles less than about 1 wt. %provide a photoresist coating that is too thin. Concentrations of themetal oxide nanoparticles greater than about 15 wt. % will provide aphotoresist composition that is too viscous and that will be difficultto provide a photoresist coating of uniform thickness on the substrate.

In some embodiments, the metal oxide nanoparticles are complexed with aligand. In some embodiments, the ligand is a carboxylic acid or sulfonicacid ligand. For example, in some embodiments, zirconium oxide orhafnium oxide nanoparticles are complexed with methacrylic acid forminghafnium methacrylic acid (HfMAA) or zirconium methacrylic acid (ZrMAA).In some embodiments, the metal oxide nanoparticles are complexed withligands including aliphatic or aromatic groups. The aliphatic oraromatic groups may be unbranched or branched with cyclic or noncyclicsaturated pendant groups containing 1-9 carbons, including alkyl groups,alkenyl groups, and phenyl groups. The branched groups may be furthersubstituted with oxygen or halogen. In some embodiments, the ligandconcentration is about 10 wt. % to about 40 wt. % based on the weight onthe metal oxide nanoparticles. At concentrations of the ligand belowabout 10 wt. % the concentration of the ligand is insufficient tocomplex the metal oxide nanoparticles. Concentrations of the ligandabove about 40 wt. % do not provide a significant improvement incomplexing the metal oxide nanoparticles over concentrations of theligand at about 40 wt. %.

In some embodiments, the metal oxide/ligand complexes are formed of acluster including metallic core having a metal with high EUV absorption,such as Cs, Ba, La, Ce, In, Sn, Ag, or Sb combined with oxygen and/ornitrogen to form 1 to 12 metal core-clusters. The metallic core-clustersare complexed with ligands including aliphatic or aromatic groups. Thealiphatic or aromatic groups may be unbranched or branched with cyclicor noncyclic saturated pendant groups containing 1-9 carbons, includingalkyl groups, alkenyl groups, and phenyl groups. The branched groups maybe further substituted with oxygen or halogen in some embodiments.

Examples of suitable metal oxide/ligand complexes according toembodiments of the disclosure are:

In some embodiments, the ligand is HfMAA or ZrMAA dissolved at about a 5wt. % to about 10 wt. % weight range in a coating solvent, such aspropylene glycol methyl ether acetate (PGMEA).

In some embodiments, an acid having an acid dissociation constant, pKa,of −15<pKa<4, or a base having a pKa of 40>pKa>9 is included in thephotoresist composition as a ligand stabilizer to stabilize the ligand.The ligand stabilizer inhibits the ligand from separating from themetal/ligand complex. The ligand stabilizer maintains a uniformconcentration of metal oxide nanoparticles in the photoresistcomposition.

The acid dissociation constant, pK_(a), is the logarithmic constant ofthe acid dissociation constant K_(a). K_(a) is a quantitative measure ofthe strength of an acid in solution. K_(a) is the equilibrium constantfor the dissociation of a generic acid according to the equation

HA+H₂O↔A⁻+H₃O⁺,

where HA dissociates into its conjugate base, A⁻, and a hydrogen ionwhich combines with a water molecule to form a hydronium ion. Thedissociation constant can be expressed as a ratio of the equilibriumconcentrations:

$K_{a} = {\frac{\left\lbrack A^{-} \right\rbrack \left\lbrack {H_{3}O^{+}} \right\rbrack}{\lbrack{HA}\rbrack\left\lbrack {H_{2}O} \right\rbrack}.}$

In most cases, the amount of water is constant and the equation can besimplified to HAχA⁻+H⁺, and

$K_{a} = {\frac{\left\lbrack A^{-} \right\rbrack \left\lbrack H^{+} \right\rbrack}{\lbrack{HA}\rbrack}.}$

The logarithmic constant, pK_(a) is related to K_(a) by the equationpK_(a)=−log₁₀(K_(a)). The lower the value of pK_(a) the stronger theacid. Conversely, the higher the value of pK_(a) the stronger the base.In some embodiments, the amount of the acid or base ranges from about0.001 wt. % to about 20 wt. % based on the total weight of thephotoresist composition. In some embodiments, the amount of acid or baseranges from about 0.1 wt. % to about 15 wt. % based on the total weightof the photoresist composition. In some embodiments, the amount of acidor base ranges from about 1 wt. % to about 10 wt. % based on the totalweight of the photoresist composition.

In some embodiments, the ligand stabilizer is an acid selected from thegroup consisting of ethanedioic acid, methanoic acid, 2-hydroxypropanoicacid, 2-hydroxybutanedioic acid, citric acid, uric acid,trifluoromethanesulfonic acid, benzenesulfonic acid, ethanesulfonicacid, methanesulfonic acid, oxalic acid, maleic acid, carbonic acid,HNO₃, H₂SO₄, HCl, oxoethanoic acid, 2-hydroxyethanoic acid, propanedioicacid, butanedioic acid, 3-oxobutanoic acid, hydroxylamine-O-sulfonicacid, formamidine sulfinic acid, methylsulfamic acid, sulfoacetic acid,1,1,2,2-tetrafluoroethanesuffonic acid, 1,3-propanedisulfonic acid,nonafluorobutane-1-sulfonic acid, 5-sulfosalicylic acid, andcombinations thereof. In some embodiments, the ligand stabilizer is abase selected from the group consisting of monoethanolamine,monoisopropanolamine, 2-amino-2-methyl-1-propanol, 1H-benzotriazole,1,2,4-triazole, 1,8-diazabicycloundec-7-ene, tetrabutylammoniumhydroxide, tetramethylammonium hydroxide, ammonium hydroxide, ammoniumsulfamate, ammonium carbamate, tetraethylammonium hydroxide,tetrapropylammonium hydroxide, and combinations thereof.

In some embodiments, the polymer resins and the PACs, along with anydesired additives or other agents, are added to the solvent forapplication. Once added, the mixture is then mixed in order to achieve ahomogenous composition throughout the photoresist to ensure that thereare no defects caused by uneven mixing or nonhomogenous composition ofthe photoresist. Once mixed together, the photoresist may either bestored prior to its usage or used immediately.

Once ready, the photoresist is applied onto the layer to be patterned,as shown in FIG. 2, such as the substrate 10 to form a photoresist layer15. In some embodiments, the photoresist is applied using a process suchas a spin-on coating process, a dip coating method, an air-knife coatingmethod, a curtain coating method, a wire-bar coating method, a gravurecoating method, a lamination method, an extrusion coating method,combinations of these, or the like. In some embodiments, the photoresistlayer 15 thickness ranges from about 10 nm to about 300 nm.

After the photoresist layer 15 has been applied to the substrate 10, apre-bake of the photoresist layer is performed in some embodiments tocure and dry the photoresist prior to radiation exposure (see FIG. 1).The curing and drying of the photoresist layer 15 removes the solventcomponent while leaving behind the polymer resin, the PACs, thecross-linking agent, and the other chosen additives. In someembodiments, the pre-baking is performed at a temperature suitable toevaporate the solvent, such as between about 50° C. and 250° C.,although the precise temperature depends upon the materials chosen forthe photoresist. The pre-baking is performed for a time sufficient tocure and dry the photoresist layer, such as between about 10 seconds toabout 10 minutes.

FIG. 3 illustrates a selective exposure of the photoresist layer to forman exposed region 50 and an unexposed region 15. In some embodiments,the exposure to radiation is carried out by placing the photoresistcoated substrate in a photolithography tool. The photolithography toolincludes a photomask 30, optics, an exposure radiation source to providethe radiation 45 for exposure, and a movable stage for supporting andmoving the substrate under the exposure radiation.

In some embodiments, the radiation source (not shown) supplies radiation45, such as ultraviolet light, to the photoresist layer 15 in order toinduce a reaction of the PACs, which in turn reacts with the polymerresin to chemically alter those regions of the photoresist layer towhich the radiation 45 impinges. In some embodiments, the radiation iselectromagnetic radiation, such as g-line (wavelength of about 436 nm),i-line (wavelength of about 365 nm), ultraviolet radiation, farultraviolet radiation, extreme ultraviolet, electron beams, or the like.In some embodiments, the radiation source is selected from the groupconsisting of a mercury vapor lamp, xenon lamp, carbon arc lamp, a KrFexcimer laser light (wavelength of 248 nm), an ArF excimer laser light(wavelength of 193 nm), an F₂ excimer laser light (wavelength of 157nm), or a CO₂ laser-excited Sn plasma (extreme ultraviolet, wavelengthof 13.5 nm).

In some embodiments, optics (not shown) are used in the photolithographytool to expand, reflect, or otherwise control the radiation before orafter the radiation 45 is patterned by the photomask 30. In someembodiments the optics include one or more lenses, mirrors, filters, andcombinations thereof to control the radiation 45 along its path.

In an embodiment, the patterned radiation 45 is extreme ultravioletlight having a 13.5 nm wavelength, the PAC is a photoacid generator, thegroup to be decomposed is a carboxylic acid group on the hydrocarbonstructure, and a cross linking agent is used. The patterned radiation 45impinges upon the photoacid generator, the photoacid generator absorbsthe impinging patterned radiation 45. This absorption initiates thephotoacid generator to generate a proton (e.g., a H⁺ atom) within thephotoresist layer 15. When the proton impacts the carboxylic acid groupon the hydrocarbon structure, the proton reacts with the carboxylic acidgroup, chemically altering the carboxylic acid group and altering theproperties of the polymer resin in general. The carboxylic acid groupthen reacts with the cross-linking agent to cross-link with otherpolymer resins within the exposed region of the photoresist layer 15.

In some embodiments, the exposure of the photoresist layer 15 uses animmersion lithography technique. In such a technique, an immersionmedium (not shown) is placed between the final optics and thephotoresist layer, and the exposure radiation 45 passes through theimmersion medium.

After the photoresist layer 15 has been exposed to the exposureradiation 45, a post-exposure baking is performed in some embodiments toassist in the generating, dispersing, and reacting of the acid/base/freeradical generated from the impingement of the radiation 45 upon the PACsduring the exposure. Such thermal assistance helps to create or enhancechemical reactions which generate chemical differences between theexposed region 50 and the unexposed region 52 within the photoresistlayer 15. These chemical differences also cause differences in thesolubility between the exposed region 50 and the unexposed region 52. Insome embodiments, the post-exposure baking occurs at temperaturesranging from about 50° C. to about 160° C. for a period of between about20 seconds and about 120 seconds.

The inclusion of the cross-linking agent into the chemical reactionshelps the components of the polymer resin (e.g., the individualpolymers) react and bond with each other, increasing the molecularweight of the bonded polymer in some embodiments. In particular, aninitial polymer has a side chain with a carboxylic acid protected by oneof the groups to be removed/acid labile groups. The groups to be removedare removed in a de-protecting reaction, which is initiated by a protonH⁺ generated by, e.g., the photoacid generator during either theexposure process or during the post-exposure baking process. The H⁺first removes the groups to be removed/acid labile groups and anotherhydrogen atom may replace the removed structure to form a de-protectedpolymer. Once de-protected, a cross-linking reaction occurs between twoseparate de-protected polymers that have undergone the de-protectingreaction and the cross-linking agent in a cross-linking reaction. Inparticular, hydrogen atoms within the carboxylic groups formed by thede-protecting reaction are removed and the oxygen atoms react with andbond with the cross-linking agent. This bonding of the cross-linkingagent to two polymers bonds the two polymers not only to thecross-linking agent but also bonds the two polymers to each otherthrough the cross-linking agent, thereby forming a cross-linked polymer.

By increasing the molecular weight of the polymers through thecross-linking reaction, the new cross-linked polymer becomes lesssoluble in conventional organic solvent negative resist developers.

Development is performed using a solvent. In some embodiments wherepositive tone development is desired, a positive tone developer such asa basic aqueous solution is used to remove regions 50 of the photoresistexposed to radiation. In some embodiments, the positive tone developer57 includes one or more selected from tetramethylammonium hydroxide(TMAH), tetrabutylammonium hydroxide, sodium hydroxide, potassiumhydroxide, sodium carbonate, sodium bicarbonate, sodium silicate, sodiummetasilicate, aqueous ammonia, monomethylamine, dimethylamine,trimethylamine, monoethylamine, diethylamine, triethylamine,monoisopropylamine, diisopropylamine, triisopropylamine, monobutylamine,dibutylamine, monoethanolamine, diethanolamine, triethanolamine,dimethylaminoethanol, diethylaminoethanol, ammonia, caustic soda,caustic potash, sodium metasilicate, potassium metasilicate, sodiumcarbonate, tetraethylammonium hydroxide, combinations of these, or thelike.

In some embodiments where negative tone development is desired, anorganic solvent or critical fluid is used to remove the unexposedregions 52 of the photoresist. In some embodiments, the negative tonedeveloper 57 includes one or more selected from hexane, heptane, octane,toluene, xylene, dichloromethane, chloroform, carbon tetrachloride,trichloroethylene, and like hydrocarbon solvents; critical carbondioxide, methanol, ethanol, propanol, butanol, and like alcoholsolvents; diethyl ether, dipropyl ether, dibutyl ether, ethyl vinylether, dioxane, propylene oxide, tetrahydrofuran, cellosolve, methylcellosolve, butyl cellosolve, methyl carbitol, diethylene glycolmonoethyl ether and like ether solvents; acetone, methyl ethyl ketone,methyl isobutyl ketone, isophorone, cyclohexanone and like ketonesolvents; methyl acetate, ethyl acetate, propyl acetate, butyl acetateand like ester solvents; pyridine, formamide, and N,N-dimethyl formamideor the like.

In some embodiments, the developer 57 is applied to the protective layerand photoresist layer 15 using a spin-on process. In the spin-onprocess, the developer 57 is applied to the photoresist layer 15 by adispenser 62 from above while the coated substrate is rotated, as shownin FIG. 4. In the case of a positive resist, the exposed region 50 ofthe photoresist layer is removed, and in the case of a negative resistthe unexposed regions 52 of the photoresist layer are removed. In someembodiments the developer 57 is supplied at a rate of between about 5ml/min and about 800 ml/min, while the coated substrate 10 is rotated ata speed of between about 100 rpm and about 2000 rpm. In someembodiments, the developer is at a temperature of between about 10° C.and about 80° C. The development operation continues for between about30 seconds to about 10 minutes in some embodiments.

While the spin-on operation is one suitable method for developing thephotoresist layer 15 after exposure, it is intended to be illustrativeand is not intended to limit the embodiment. Rather, any suitabledevelopment operations, including dip processes, puddle processes, andspray-on methods, may alternatively be used. All such developmentoperations are included within the scope of the embodiments.

In some embodiments, the photoresist developers 57 dissolve thecross-linked, radiation-exposed portions 50 of the photoresist layer 15.

In some embodiments, the photoresist developer 57 includes a majorsolvent, an acid or a base, and a chelate, as described in U.S.application Ser. No. 15/938,599, incorporated by reference in itsentirety. In some embodiments, the concentration of the major solvent isfrom about 60 wt. % to about 99 wt. % based on the total weight of thephotoresist developer. The acid or base concentration is from about0.001 wt. % to about 20 wt. % based on the total weight of thephotoresist developer. In certain embodiments, the acid or baseconcentration in the developer is from about 0.01 wt. % to about 15 wt.% based on the total weight of the photoresist developer. The chelateconcentration is from about 0.001 wt. % to about 20 wt. % of the totalweight of the photoresist developer. In certain embodiments, theconcentration of the chelate ranges from about 0.01 wt. % to about 15wt. % based on the total weight of the photoresist developer.

In some embodiments, the major solvent has Hansen solubility parametersof 15<δ_(d)<25, 10<δ_(p)<25, and 6<δ_(h)<30. The units of the Hansensolubility parameters are (Joules/cm³)^(1/2) or, equivalently, MPa^(1/2)and are based on the idea that one molecule is defined as being likeanother if it bonds to itself in a similar way. δ_(d) is the energy fromdispersion forces between molecules. δ_(p) is the energy from dipolarintermolecular force between the molecules. δ_(h) is the energy fromhydrogen bonds between molecules. The three parameters, δ_(d), δ_(p),and δ_(h), can be considered as coordinates for a point in threedimensions, known as the Hansen space. The nearer two molecules are inHansen space, the more likely they are to dissolve into each other.

Solvents having the desired Hansen solubility parameters includedimethyl sulfoxide, acetone, ethylene glycol, methanol, ethanol,propanol, propanediol, water, 4-methyl-2-pentanone, hydrogen peroxide,isopropanol, and butyldiglycol.

In some embodiments, suitable acids for the photoresist developer 57include an organic acid selected from the group consisting ofethanedioic acid, methanoic acid, 2-hydroxypropanoic acid,2-hydroxybutanedioic acid, citric acid, uric acid,trifluoromethanesulfonic acid, benzenesulfonic acid, ethanesulfonicacid, methanesulfonic acid, oxalic acid, maleic acid, carbonic acid,oxoethanoic acid, 2-hydroxyethanoic acid, propanedioic acid, butanedioicacid, 3-oxobutanoic acid, hydroxylamine-o-sulfonic acid, formamidinesulfinic acid, methylsulfamic acid, sulfoacetic acid,1,1,2,2-tetrafluoroethanesulfonic acid, 1,3-propanedisulfonic acid,nonafluorobutane-1-sulfonic acid, 5-sulfosalicylic acid, andcombinations thereof. In some embodiments, the acid is an inorganic acidselected from the group consisting of nitric acid, sulfuric acid,hydrochloric acid, and combinations thereof.

In some embodiments, suitable bases for the photoresist developer 57include an organic base selected from the group consisting ofmonoethanolamine, monoisopropanolamine, 2-amino-2-methyl-1-propanol,1H-benzotriazole, 1,2,4-triazole, 1,8-diazabicycloundec-7-ene,tetrabutyl ammonium hydroxide, tetramethylammonium hydroxide, ammoniumhydroxide, ammonium sulfamate, ammonium carbamate, tetraethylammoniumhydroxide, tetrapropylammonium hydroxide, and combinations thereof.

In some embodiments, the chelate is selected from the group consistingof ethylenediaminetetraacetic acid (EDTA),ethylenediamine-N,N′-disuccinic acid (EDDS),diethylenetriaminepentaacetic acid (DTPA), polyaspartic acid,trans-1,2-cyclohexanediamine-N,N,N′,N′-tetraacetic acid monohydrate,ethylenediamine, and combinations thereof, or the like.

In an embodiment, the photoresist developer 57 includes an additionalsolvent. In some embodiments, the additional solvent includes water;hexane, heptane, octane, toluene, xylene, dichloromethane, chloroform,carbon tetrachloride, trichloroethylene, and like hydrocarbon solvents;critical carbon dioxide, methanol, ethanol, propanol, butanol, and likealcohol solvents; diethyl ether, dipropyl ether, dibutyl ether, ethylvinyl ether, dioxane, propylene oxide, tetrahydrofuran, cellosolve,methyl cellosolve, butyl cellosolve, methyl carbitol, diethylene glycolmonoethyl ether and like ether solvents; acetone, methyl ethyl ketone,methyl isobutyl ketone, isophorone, cyclohexanone and like ketonesolvents; methyl acetate, ethyl acetate, propyl acetate, butyl acetateand like ester solvents; pyridine, formamide, and N,N-dimethyl formamideor the like. In an embodiment, the concentration of the additionalsolvent is from about 1 wt. % to about 40 wt. % based on the totalweight of the developer.

In some embodiments, the photoresist developer 57 includes hydrogenperoxide in a concentration of up to about 10 wt. % based on the totalweight of the developer.

In some embodiments, the photoresist developer 57 includes up to about 1wt. % of a surfactant to increase the solubility and reduce the surfacetension on the substrate. In some embodiments, the surfactant isselected from the group consisting of alkylbenzenesulfonates, ligninsulfonates, fatty alcohol ethoxylates, and alkylphenol ethoxylates. Insome embodiments, the surfactant is selected from the group consistingof sodium stearate, 4-(5-dodecyl) benzenesulfonate, ammonium laurylsulfate, sodium lauryl sulfate, sodium laureth sulfate, sodium myrethsulfate, dioctyl sodium sulfosuccinate, perfluorooctanesulfonate,perfluorobutanesulfonate, alkyl-aryl ether phosphate, alkyl etherphosphates, sodium lauroyl sarcosinate, perfluoronononanoate,perfluorooctanoate, octenidine dihydrochloride, cetrimonium bromide,cetylpyridinium chloride, benzalkonium chloride, benzethonium chloride,dimethyldioctadecylammonium chloride, dioctadecyldimethylammoniumbromide, 3-[(3-cholamidopropyedimethylammonio]-1-propanesulfonate,cocamidopropyl hydroxysultaine, cocamidopropyl betaine,phospholipidsphosphatidylserine, phosphatidylethanolamine,phosphatidylcholine, sphingomyelins, octaethylene glycol monodecylether, pentaethylene glycol monodecyl ether, polyethoxylated tallowamine, cocamide monoethanolamine, cocamide diethanolamine, glycerolmonostearate, glycerol monolaurate, sorbitan monolaurate, sorbitanmonostearate, sorbitan tristearate, and combinations thereof.

During the development process, the developer 57 dissolves the radiationexposed regions 50 of the cross-linked negative resist, exposing thesurface of the substrate 10, as shown in FIG. 5, and leaving behindwell-defined unexposed photoresist regions 52, having improveddefinition than provided by conventional negative photoresistphotolithography.

After the developing operation S150, remaining developer is removed fromthe patterned photoresist covered substrate. The remaining developer isremoved using a spin-dry process in some embodiments, although anysuitable removal technique may be used. After the photoresist layer 15is developed, and the remaining developer is removed, additionalprocessing is performed while the patterned photoresist layer 52 is inplace. For example, an etching operation, using dry or wet etching, isperformed in some embodiments, to transfer the pattern of thephotoresist layer 52 to the underlying substrate 10, forming recesses55′ as shown in FIG. 6. The substrate 10 has a different etch resistancethan the photoresist layer 15. In some embodiments, the etchant is moreselective to the substrate 10 than the photoresist layer 15.

In some embodiments, the substrate 10 and the photoresist layer 15contain at least one etching resistance molecule. In some embodiments,the etching resistant molecule includes a molecule having a low Onishinumber structure, a double bond, a triple bond, silicon, siliconnitride, titanium, titanium nitride, aluminum, aluminum oxide, siliconoxynitride, combinations thereof, or the like.

In some embodiments, a layer to be patterned 60 is disposed over thesubstrate prior to forming the photoresist layer, as shown in FIG. 8. Insome embodiments, the layer to be patterned 60 is a metallization layeror a dielectric layer, such as a passivation layer, disposed over ametallization layer. In embodiments where the layer to be patterned 60is a metallization layer, the layer to be patterned 60 is formed of aconductive material using metallization processes, and metal depositiontechniques, including chemical vapor deposition, atomic layerdeposition, and physical vapor deposition (sputtering). Likewise, if thelayer to be patterned 60 is a dielectric layer, the layer to bepatterned 60 is formed by dielectric layer formation techniques,including thermal oxidation, chemical vapor deposition, atomic layerdeposition, and physical vapor deposition.

The photoresist layer 50 is subsequently selectively exposed to actinicradiation 45 to form exposed regions 50 and unexposed regions 52 in thephotoresist layer, as shown in FIG. 9, and described herein in relationto FIG. 3. As explained herein the photoresist is a negativephotoresist, wherein polymer crosslinking occurs in the exposed regions50 in some embodiments.

As shown in FIG. 10, the exposed photoresist regions 50 are developed bydispensing developer 57 from a dispenser 62 to form a pattern ofphotoresist openings 55, as shown in FIG. 11. The development operationis similar to that explained with reference to FIGS. 4 and 5, herein.

Then as shown in FIG. 12, the pattern 55 in the photoresist layer 15 istransferred to the layer to be patterned 60 using an etching operationand the photoresist layer is removed, as explained with reference toFIG. 6 to form pattern 55″ in the layer to be patterned 60.

In some embodiments, the selective exposure of the photoresist layer 15to form exposed regions 50 and unexposed regions 52 is performed usingextreme ultraviolet lithography. In an extreme ultraviolet lithographyoperation a reflective photomask 65 is used to form the patternedexposure light, as shown in FIG. 13. The reflective photomask 65includes a low thermal expansion glass substrate 70, on which areflective multilayer 75 of Si and Mo is formed. A capping layer 80 andabsorber layer 85 are formed on the reflective multilayer 75. A rearconductive layer 90 is formed on the back side of the low thermalexpansion substrate 70. In extreme ultraviolet lithography, extremeultraviolet radiation 95 is directed towards the reflective photomask 65at an incident angle of about 6°. A portion 97 of the extremeultraviolet radiation is reflected by the Si/Mo multilayer 75 towardsthe photoresist coated substrate 10, while the portion of the extremeultraviolet radiation incident upon the absorber 85 is absorbed by thephotomask. In some embodiments, additional optics, including mirrors arebetween the reflective photomask 65 and the photoresist coatedsubstrate.

The novel photoresist composition and photolithography techniquesaccording to the present disclosure provide improved critical dimensionvariation, smoother photoresist profile, and reduced defects.Photoresist compositions and photolithography techniques according tothe present disclosure inhibit photoresist aging. The shelf life ofphotoresist compositions according to the present disclosure can have agreater than 50% longer shelf life than other photoresist compositions.In some embodiments, the shelf life of the photoresist composition isincreased by 100%. In some embodiments, the shelf life of thephotoresist increases from 2 weeks to 4 weeks. Use of the disclosedphotoresist composition can reduce semiconductor processing costs, asphotoresist waste is reduced.

An embodiment of the disclosure is a photoresist composition including aphotoresist material including metal oxide nanoparticles and a ligand,and an acid having an acid dissociation constant, pKa, of −15<pKa<4, ora base having a pKa of 40>pKa>9. In an embodiment, the amount of theacid or base ranges from 0.001 wt. % to 20 wt. % based on the totalweight of the photoresist composition. In an embodiment, the amount ofmetal oxide nanoparticles ranges from 1 wt. % to 10 wt. % based on thetotal weight of the photoresist composition. In an embodiment, the metaloxide nanoparticles have an average particle size ranging from 1 nm to10 nm. In an embodiment, the metal oxide nanoparticles are selected fromthe group consisting of titanium dioxide, zinc oxide, zirconium dioxide,nickel oxide, cobalt oxide, manganese oxide, copper oxides, iron oxides,strontium titanate, tungsten oxides, vanadium oxides, chromium oxides,tin oxides, hafnium oxide, indium oxide, cadmium oxide, molybdenumoxide, tantalum oxides, niobium oxide, aluminum oxide, and combinationsthereof. In an embodiment, the ligand is a carboxylic acid or sulfonicacid ligand. In an embodiment, the photoresist includes a polymer resinand a photoactive compound.

Another embodiment of the disclosure is a photoresist compositionincluding a photoresist material including metal oxide nanoparticles anda ligand, and a ligand stabilizer. In an embodiment, the ligandstabilizer is selected from the group consisting of ethanedioic acid,methanoic acid, 2-hydroxypropanoic acid, 2-hydroxybutanedioic acid,citric acid, uric acid, trifluoromethanesulfonic acid, benzenesulfonicacid, ethanesulfonic acid, methanesulfonic acid, oxalic acid, maleicacid, carbonic acid, HNO₃, H₂SO₄, HCl, oxoethanoic acid,2-hydroxyethanoic acid, propanedioic acid, butanedioic acid,3-oxobutanoic acid, hydroxylamine-O-sulfonic acid, formamidine sulfinicacid, methylsulfamic acid, sulfoacetic acid,1,1,2,2-tetrafluoroethanesulfonic acid, 1,3-propanedisulfonic acid,nonafluorobutane-1-sulfonic acid, 5-sulfosalicylic acid,monoethanolamine, monoisopropanolamine, 2-amino-2-methyl-1-propanol,1H-benzotriazole, 1,2,4-triazole, 1,8-diazabicycloundec-7-ene,tetrabutylammonium hydroxide, tetramethylammonium hydroxide, ammoniumhydroxide, ammonium sulfamate, ammonium carbamate, tetraethylammoniumhydroxide, tetrapropylammonium hydroxide, and combinations thereof. Inan embodiment, the amount of the ligand stabilizer ranges from 0.001 wt.% to 20 wt. % based on the total weight of the photoresist composition.In an embodiment, the amount of metal oxide nanoparticles ranges from 1wt. % to 10 wt. % based on the total weight of the photoresistcomposition. In an embodiment, the photoresist composition furtherincludes a polymer resin and a photoactive compound. In an embodiment,the polymer resin includes one or more groups that will decompose whenexposed to or react with bases, acids, or free radicals generated by thephotoactive compound. In an embodiment, the photoactive compound is aphotoacid generator, photobase generator, or a free-radical generator.In an embodiment, the photoresist composition includes from 0.001 wt. %to 1 wt. % of a surfactant.

Another embodiment of the disclosure is a method of forming aphotoresist pattern including forming a photoresist layer comprising aphotoresist composition over a substrate. The photoresist layer isselectively exposed to actinic radiation. The selectively exposedphotoresist layer is developed to form a pattern in the photoresistlayer. The photoresist composition includes metal oxide nanoparticles, aligand, and an acid having an acid dissociation constant, pKa, of−15<pKa<4, or a base having a pKa of 40>pKa>9. In an embodiment, theactinic radiation is extreme ultraviolet radiation. In an embodiment,the photoresist composition includes a polymer resin and a photoactivecompound. In an embodiment, the polymer resin includes one or moregroups that will decompose when exposed to or react with bases, acids,or free radicals generated by the photoactive compound, and thephotoactive compound is a photoacid generator, photobase generator, or afree-radical generator. In an embodiment, the method includes heatingthe photoresist layer after selectively exposing the photoresist layer.

The foregoing outlines features of several embodiments or examples sothat those skilled in the art may better understand the aspects of thepresent disclosure. Those skilled in the art should appreciate that theymay readily use the present disclosure as a basis for designing ormodifying other processes and structures for carrying out the samepurposes and/or achieving the same advantages of the embodiments orexamples introduced herein. Those skilled in the art should also realizethat such equivalent constructions do not depart from the spirit andscope of the present disclosure, and that they may make various changes,substitutions, and alterations herein without departing from the spiritand scope of the present disclosure.

What is claimed is:
 1. A photoresist composition, comprising: aphotoresist material including metal oxide nanoparticles and a ligand;and an acid having an acid dissociation constant, pKa, of −15<pKa<4, ora base having a pKa of 40>pKa>9.
 2. The photoresist composition of claim1, wherein the amount of the acid or base ranges from 0.001 wt. % to 20wt. % based on the total weight of the photoresist composition.
 3. Thephotoresist composition of claim 1, wherein the amount of metal oxidenanoparticles ranges from 1 wt. % to 10 wt. % based on the total weightof the photoresist composition.
 4. The photoresist composition of claim1, wherein the metal oxide nanoparticles have an average particle sizeranging from 1 nm to 10 nm.
 5. The photoresist composition of claim 1,wherein the metal oxide nanoparticles are selected from the groupconsisting of titanium dioxide, zinc oxide, zirconium dioxide, nickeloxide, cobalt oxide, manganese oxide, copper oxides, iron oxides,strontium titanate, tungsten oxides, vanadium oxides, chromium oxides,tin oxides, hafnium oxide, indium oxide, cadmium oxide, molybdenumoxide, tantalum oxides, niobium oxide, aluminum oxide, and combinationsthereof.
 6. The photoresist composition of claim 1, wherein the ligandis a carboxylic acid or sulfonic acid ligand.
 7. The photoresistcomposition of claim 1, further comprising a polymer resin and aphotoactive compound.
 8. A photoresist composition, comprising: aphotoresist material including metal oxide nanoparticles and a ligand;and a ligand stabilizer.
 9. The photoresist composition of claim 1,wherein the ligand stabilizer is selected from the group consisting ofethanedioic acid, methanoic acid, 2-hydroxypropanoic acid,2-hydroxybutanedioic acid, citric acid, uric acid,trifluoromethanesulfonic acid, benzenesulfonic acid, ethanesulfonicacid, methanesulfonic acid, oxalic acid, maleic acid, carbonic acid,HNO₃, H₂SO₄, HCl, oxoethanoic acid, 2-hydroxyethanoic acid, propanedioicacid, butanedioic acid, 3-oxobutanoic acid, hydroxylamine-O-sulfonicacid, formamidine sulfinic acid, methylsulfamic acid, sulfoacetic acid,1,1,2,2-tetrafluoroethanesulfonic acid, 1,3-propanedisulfonic acid,nonafluorobutane-1-sulfonic acid, 5-sulfosalicylic acid,monoethanolamine, monoisopropanolamine, 2-amino-2-methyl-1-propanol,1H-benzotriazole, 1,2,4-triazole, 1,8-diazabicycloundec-7-ene,tetrabutylammonium hydroxide, tetramethylammonium hydroxide, ammoniumhydroxide, ammonium sulfamate, ammonium carbamate, tetraethylammoniumhydroxide, tetrapropylammonium hydroxide, and combinations thereof. 10.The photoresist composition of claim 8, wherein the amount of the ligandstabilizer ranges from 0.001 wt. % to 20 wt. % based on the total weightof the photoresist composition.
 11. The photoresist composition of claim8, wherein the amount of metal oxide nanoparticles ranges from 1 wt. %to 10 wt. % based on the total weight of the photoresist composition.12. The photoresist composition of claim 8, further comprising a polymerresin and a photoactive compound.
 13. The photoresist composition ofclaim 12, wherein the polymer resin includes one or more groups thatwill decompose when exposed to or react with bases, acids, or freeradicals generated by the photoactive compound.
 14. The photoresistcomposition of claim 13, wherein the photoactive compound is a photoacidgenerator, photobase generator, or a free-radical generator.
 15. Thephotoresist composition of claim 8, further comprising from 0.001 wt. %to 1 wt. % of a surfactant.
 16. A method of forming a photoresistpattern, comprising: forming a photoresist layer comprising aphotoresist composition over a substrate; selectively exposing thephotoresist layer to actinic radiation; and developing the photoresistlayer to form a pattern in the photoresist layer; wherein thephotoresist composition includes: metal oxide nanoparticles; a ligand;and an acid having an acid dissociation constant, pKa, of −15<pKa<4, ora base having a pKa of 40>pKa>9.
 17. The method according to claim 16,wherein the actinic radiation is extreme ultraviolet radiation.
 18. Themethod according to claim 16, wherein the photoresist compositionfurther comprises a polymer resin and a photoactive compound.
 19. Themethod according to claim 18, wherein the polymer resin includes one ormore groups that will decompose when exposed to or react with bases,acids, or free radicals generated by the photoactive compound; and thephotoactive compound is a photoacid generator, photobase generator, or afree-radical generator.
 20. The method according to claim 16, furthercomprising extending the pattern in the photoresist layer into thesubstrate.